This invention relates to an apparatus for mitigating the recoil of projectile-firing devices and methods thereof. More particularly, the present invention relates to utilizing friction for mitigating the recoil of projectile-firing devices designed to disarm explosives devices, commonly known in the art as an explosives disrupters. Even more particularly, the present invention relates to using friction for mitigating the recoil of projectile-firing devices attached to remote-control robots or robot arms, often used by law enforcement agencies and others for remotely disarming explosives devices.
In any gun system, or more generally, projectile-firing device, conservation of momentum provides that the momentum carried by the projectile and the gases is equal to, but in the opposite direction of, the momentum imparted to the device. The momentum imparted to the device is, in turn, equal to the recoil force integrated over time, or the impulse. This is commonly referred to as the xe2x80x9ckickxe2x80x9d experienced when a device is fired. While the total amount of momentum for a given projectile fired at a given velocity cannot be changed, it can be managed. The force-time profile can be changed from a very high, short-lived force, to a longer, much lower amplitude force pulse.
Present recoil-mitigation devices utilize complex and expensive hydraulics, pneumatics, pistons, springs, friction, or some combination thereof. In addition, present devices are integral to the projectile-firing device and, therefore, not always easily or quickly adaptable to varying situations. Examples include U.S. Pat. Nos. 4,514,921 (coil spring compression), 4,656,921 (hydraulic fluid), 4,972,760 (adjustable recoil spring), 5,353,681 (recoil spring, friction, and pneumatics), and 5,617,664 (recoil spring).
In the particular case of some explosives disrupters, there may be no recoil mitigation. Disrupter devices are typically attached to a support frame mounted on the ground or mounted on a remote-controlled robot, whereby the device can be triggered from a relatively safe distance to fire a projectile into an article suspected of containing a bomb or other explosives. Such devices are generally of a single-shot design and produce a significant impulsexe2x80x94oftentimes sufficient to propel the support frame/robot backwards, cause it to topple over, and/or sustain significant damage. Depending upon the situation, such devices may be called upon to fire a variety of projectiles at a variety of velocities from a variety of support frame/robots. This in turn creates a variety of recoil forces requiring, in turn, a variety of recoil mitigation solutions tailored to each support frame/robot. For example, the momentum imparted to devices from a column of water, often used to disarm soft-package bombs, such as briefcase bombs, may vary from close to five pounds-force-seconds at a low velocity to over nine pounds-force-seconds at a high velocity (140 milliliter load at a velocity of 1,000 feet per second) and even as high as 12 pounds-force-seconds. It has been demonstrated that the recoil forces resulting from firing a high velocity water load reach as high as 15,000 pounds-force. Metal slugs impart momentum in the range of four pounds-force-seconds to six pounds-force-seconds.
A general rule of thumb for a device without recoil mitigation fired by a human is that the momentum should not exceed three pounds-force-seconds. By comparison, the momentum carried by a 150 grain projectile fired from a 30-06 rifle at a velocity of 2,810 feet per second is approximately 1.87 pounds-force-seconds. Thus, the momentum generated by an explosives disrupter can be relatively significant.
It is also important that the recoil system not appreciably affect the performance of the disrupter or its projectiles. Procedures have been developed over the years that allow users to successfully disrupt a variety of suspected bombs, and a recoil system that forces users to adjust techniques is not desirable.
Therefore, there is a need for a recoil-mitigation device which overcomes these disadvantages.
According to the present invention, a recoil mitigation apparatus and method is provided. The apparatus includes a brake assembly, comprising at least one brake shoe, adapted to enable frictional braking force to be imposed, directly or indirectly, upon a projectile-firing device, such that when the device is fired, the friction created mitigates the recoil of the device. In a preferred embodiment, the projectile-firing device is secured within a tube to form a firing assembly. The firing assembly is placed within the brake assembly, the at least one brake shoe of the brake assembly frictionally contacting the tube with force supplied by a spring-loaded clamp or similar device. The brake assembly is further restrained, for example, by a remote-control robot or robot arm, such that when the firing device is fired, the firing assembly frictionally recoils but is slideably restrained by the brake assembly, whereby the recoil force is mitigated. Although a tube is preferred, to at least protect the projectile-firing device, those skilled in the art will recognize that the projectile-firing device may be placed directly within the brake assembly and the frictional contact be applied directly to the projectile-firing device itself; for example, to the barrel.